Innovative Method of Using Activated Sludge for Feed Modification in Aquaculture

The article is devoted to the development and study of an innovative method for modifying feed in aquaculture based on the use of activated sludge from biofloc technologies (BFTs). The study presents the results of an experimental study of two BFT systems created on the basis of different complexes of bacterial strains: probiotic strains (S1) and strains isolated from the bottom sediments of the Don River (S2). The effectiveness of floc-forming bacteria strains MT141 and MT142 is demonstrated, which increased the biomass of flocs within 7 days and increased the content by 5%. The dominant bacteria in the BFT, out of the total number of species, were representatives of the genus Runella (up to 33%) and the genus Exiguobacterium (up to 26%), and 20% of the floc community bacteria were groups of the Christensenellaceae R-7 group, the genus Acetoanaerobium, and the genus Bryobacter (up to 11%). The amino acid composition of the active sludge proteins in the BFT system contained a significant percentage of amino acids, such as valine, glycine, and leucine, which were comparable to the requirements for their content in crustacean feed. The effectiveness of the feed additive was evaluated on two aquatic species, Clarias gariepinus and Cherax quadricarinatus. Catfish raised using the BFT system showed high biomass growth, with a survival rate of 98% and a two-fold reduction in feed conversion ratio. Australian red claw crayfish consuming the experimental feed increased their average daily growth by 0.2%, and the protein content in their muscle tissue was three times higher than in the control group. The results of the study confirm the promise of using dried activated sludge meal as a safe and effective protein supplement for aquaculture feed.